8,440 research outputs found

### Negative Elliptic Flow from Anomaly Induced DCC Formation

We discuss characteristic experimental signatures related to the mechanism of
DCC formation triggered by the chiral U(1) anomaly in relativistic heavy ion
collisions. We predict an enhancement of the fraction of neutral pions compared
with all pions in the direction perpendicular to the scattering plane. To
quantify the effect on the angular distribution of neutral pions, we compute
the elliptic flow parameter $v_2$ as a function of the transverse momentum. We
find values of order -0.05 at small momenta for neutral pions. We also compute
the $v_2$ parameter for inclusive photons, which is easier to measure, and
confirmed that the negative a few percent effect prevails in this observable.Comment: Contribution to PANIC 200

### Charmonia above the Deconfinement Phase Transition

Analyzing correlation functions of charmonia at finite temperature ($T$) on
$32^3\times(32-96)$ anisotropic lattices by the maximum entropy method (MEM),
we find that $J/\psi$ and $\eta_c$ survive as distinct resonances in the plasma
even up to $T \simeq 1.6 T_c$ and that they eventually dissociate between $1.6
T_c$ and $1.9 T_c$ ($T_c$ is the critical temperature of deconfinement). This
suggests that the deconfined plasma is non-perturbative enough to hold
heavy-quark bound states. The importance of having sufficient number of
temporal data points in the MEM analysis is also emphasized.Comment: Lattice2003(nonzero), 3 pages, 3 figure

### Relativistic heavy ion collisions --- Where are we now? Where do we go?

Various aspects of the current status of ultrarelativistic heavy ion
collisions are reviewed. Perspectives of heavy ion physics in the future are
given as well.Comment: 8 pages, 4 postscript figures, LaTex, Invited talk presented at the
KEK-Tanashi International Symposium on ``Physics of Hadrons and Nuclei'',
Dec.14-17, 1998 Tokyo, Japan, Submitted to Nuclear Physics

### Measuring the Higgs CP property at a Photon Linear Collider

We study measurement of the CP property of the Higgs boson at a photon linear
collider. One method where we take advantage of interference between
Higgs-production and background amplitudes is proposed. A broad peak of the
photon energy spectrum is helpful in observing the energy dependence of the
interference effects. Numerical results for the process $\gamma \gamma \to t
\bar{t}$ are shown as an example.Comment: 4 pages, 1 PS figure. Talk given at the Linear Collider Workshop
2000, Fermilab, Oct. 24 - 28, 200

### Free Meson Spectral Functions on the Lattice

We present results from an analytic calculation of thermal meson spectral
functions in the infinite temperature (free field) limit. We compare spectral
functions for various lattice fermion formulations used at present in studies
of in-medium properties of hadrons based on the maximum entropy method (MEM).
In particular, we will present a new calculation of spectral functions
performed with extended quark sources.Comment: 3 pages, Lattice2003(nonzero

### Hadronic Spectral Functions above the QCD Phase Transition

We extract the spectral functions in the scalar, pseudo-scalar, vector, and
axial vector channels above the deconfinement phase transition temperature (Tc)
using the maximum entropy method (MEM). We use anisotropic lattices, 32^3 * 32,
40, 54, 72, 80, and 96 (corresponding to T = 2.3 Tc --> 0.8 Tc), with the
renormalized anisotropy xi = 4.0 to have enough temporal data points to carry
out the MEM analysis. Our result suggests that the spectral functions continue
to possess non-trivial structures even above Tc and in addition that there is a
qualitative change in the state of the deconfined matter between 1.5 Tc and 2
Tc.Comment: 3 pages, 4 figures, Lattice2002(nonzerot

### Comment on: "Transverse-Mass $M_\perp$ Dependence of Dilepton Emission from Preequilibrium and Quark-Gluon Plasma in High Energy Nucleus-Nucleus Collisions"

In a recent Letter, Geiger presents calculations of the dilepton emission
from the early stage of ultrarelativistic heavy ion collisions using the parton
cascade model (PCM). He shows that the $M_\perp$ scaling is not observed. In
this Comment, we point out that this is largely due to a defect in the PCM.Comment: 3 pages, LaTex, LBL-3526

### Probing the CP nature of the Higgs bosons by top-pair production at photon linear colliders

We study effects of heavy Higgs bosons on the top-pair production process at
photon linear colliders. The interference patterns between the resonant
Higgs-production amplitudes and the continuum QED amplitudes are examined. The
patterns tell us not only the CP nature of the Higgs bosons but also the phase
of the $\gamma\gamma$--Higgs vertex which gives new information about the Higgs
couplings to new charged particles. We point out that it is necessary to use
circularly polarized photon beams to produce efficiently heavy Higgs bosons
whose masses exceed the electron beam energy, and show that the above
interference patterns of the production amplitudes can be studied by observing
top decay angular distributions. Analytic expressions for the helicity
amplitudes for the sequential process $\gamma\gamma \to t \bar{t} \to (bW^+)
(\bar{b}W^-) \to (b f_1 \bar{f}_2) (\bar{b} f_3 \bar{f}_4)$ are presented in
terms of the generic $\gamma\gamma \to t \bar{t}$ production amplitudes.Comment: 34 pages, LATEX file with 6 PS figures, comments adde

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